title: Mechanisms associated with dose-dependent inhibition of rat mammary carcinogenesis by dry bean (Phaseolus vulgaris, L.).
abstract: The purpose of this study was to determine whether a dry bean (Phaseolus vulgaris, L.) containing diet exerts an inhibitory effect on mammary carcinogenesis in a well-characterized rodent model for breast cancer. Twenty-one-d-old female Sprague Dawley rats were given an intraperitoneal injection of 1-methyl-1-nitrosourea and 7 d after carcinogen injection were randomized to 1 of 5 groups fed a modification of the AIN-93G diet formulation containing 0, 7.5, 15, 30, or 60% (wt:wt) small red dry bean incorporated as cooked, freeze-dried, and milled powder. All experimental diets had the same macronutrient content based on proximate analysis. Compared with the control group, dry bean consumption resulted in dose-dependent reductions in mammary cancer incidence (P = 0.046), cancer multiplicity (P = 0.001), and tumor burden (P = 0.01). Dry bean consumption was associated with dose-dependent reductions in plasma concentrations of glucose, insulin, insulin-like growth factor-1, C-reactive protein, and interleukin-6 in food-deprived rats. Analysis of mammary adenocarcinomas indicated that a dominant mechanism accounting for reduced tumor burden was the induction of apoptosis. B cell lymphoma 2 and X-linked inhibitor of apoptosis protein levels decreased and BCL-2-associated X protein increased with increasing dry bean consumption, findings consistent with the induction of apoptosis via the mitochondrial pathway. These data demonstrate that a legume without noteworthy content of isoflavones inhibits the development of mammary carcinogenesis and are consistent with a recent report from the Nurses Health Study that bean or lentil intake is associated with a lower risk for breast cancer.
authors.affiliation: Cancer Prevention Laboratory, Department of Horticulture, Colorado State University, Fort Collins, CO 80523, USA.
authors.forename: Matthew D
authors.initials: MD
authors.lastname: Thompson
authors.forename: Henry J
authors.initials: HJ
authors.lastname: Thompson
authors.forename: Mark A
authors.initials: MA
authors.lastname: Brick
authors.forename: John N
authors.initials: JN
authors.lastname: McGinley
authors.forename: Weiqin
authors.initials: W
authors.lastname: Jiang
authors.forename: Zongjian
authors.initials: Z
authors.lastname: Zhu
authors.forename: Pamela
authors.initials: P
authors.lastname: Wolfe
mesh_terms: D000821:Animal Feed; D000818:Animals; D017209:Apoptosis; D049109:Cell Proliferation; D004032:Diet; D004305:Dose-Response Relationship, Drug; D005260:Female; D015674:Mammary Neoplasms, Animal / Q000139:chemically induced* / Q000517:prevention & control*; D008770:Methylnitrosourea / Q000633:toxicity; D027805:Phaseolus / Q000378:metabolism*; D051381:Rats; D017207:Rats, Sprague-Dawley
chemical_list: D008770:Methylnitrosourea